1. Field of the Invention
The present invention is directed to an air dryer cartridge, and more specifically to an air dryer cartridge having an integrated check valve.
2. Description of Related Art
The pneumatic braking system of a commercial vehicle typically has an air compressor, a governor for controlling the operating cycle of the air compressor, an air dryer and a reservoir for holding pressurized air for delivery to the pneumatic components, such as the brakes. The air compressor operates successively in a loading (compressing) mode and an unloading (non-compressing) mode.
When the pressure in the air reservoir falls below a predetermined minimum pressure, typically about 100 psig, the governor causes the air compressor to operate in the loading mode to compress air for storage in the air reservoir. Before storing the air in the air reservoir, the compressed air from the air compressor passes through an air dryer which removes moisture and contaminants therefrom. When the air reservoir reaches the desired pressure, typically about 120 psig, the governor causes the air compressor to operate in the unloading mode and causes the purge valve in the air dryer to open to atmosphere.
One type of air dryer includes a removable cartridge that dries the compressed air as it flows through the cartridge during the loading mode. During the unloading mode, when the governor causes the purge valve in the air dryer to open the inlet of the cartridge to exhaust to atmosphere, the air flow direction is reversed and previously dried compressed air is sent through the cartridge to remove moisture and contaminants from the cartridge.
A check valve is commonly used to reduce the rate of flow of air through the cartridge during the unloading mode in order to more efficiently remove moisture and contaminants from the desiccant. The check valve is frequently positioned within a housing of the air dryer, but it may also be a part of the air dryer cartridge. One type of air dryer cartridge has outer and inner shells with a seal positioned between the two to direct air flow through a preferable passage within the cartridge. The seal is not integrated with a check valve. Typically, air dryer cartridges also have two separate gaskets or seals for sealing between a base of the cartridge and an air dryer. These seals are also not integrated with a check valve.